These are the basic abilities investigators use to accomplish things in the game. Every investigator has six skills, listed below. Investigators also have a value for each of these skills, depending on how they have positioned their skill sliders. A skill value represents the number of dice the investigator rolls for a check based on that skill.
Fight: Used for physical feats of strength and endurance. Also used in combat.
Lore: Used for tests of mystic knowledge and ability. Also used in casting spells.
Luck: Used to determine the whims of chance. It is the most common skill used in encounters.
Sneak: Used for feats of stealth and thievery. Also used when evading monsters.
Speed: Used for tests of quickness and agility. Also used to determine an investigator's movement.
Will: Used to test an investigator's force of personality and willpower. Also used for Horror checks at the start of combat.
Investigators are often called upon to perform skill checks in order to avoid harm or to accomplish something in the game. When the game calls for a skill check, it is presented in a consistent format that provides the following information:
- The skill you must use to perform the check
- The modifier (bonus or penalty) to the check, if any
- he difficulty of the check (not listed if the difficulty is 1)
Example: Make a Sneak (-1) check. In this example, Sneak is the skill the investigator must use for the check. The modifier is -1, a penalty in this case. Since it is not specifically listed, the difficulty is 1.
When making a skill check, a player always rolls a number of dice equal to his investigator's value in the appropriate skill.
This number is added to or subtracted from the investigator's skill value before the player makes the check. The result is the number of dice the player rolls to make the check. Note that modifiers always apply to the number of dice a player rolls for a check, not to the results of the individual dice.
Example: Michael McGlen is asked to make the two skill checks listed in the example above. His current Sneak is 3 and his current Luck is 2. In the first example, he subtracts one from his Sneak of 3 (for the -1 modifier) and therefore rolls two dice. In the second, he adds two to his Luck of 2 (for the +2 modifier) and therefore rolls four dice.
Important: If the modifier reduces an investigator to 0 or fewer dice, he automatically fails the check. The player may still spend Clue tokens to make the check.
This is the number of successes an investigator must roll during a skill check to pass the check. Each die result of 5 or 6 counts as one success. Remember that if a skill check does not list a difficulty, it is assumed to be 1.
Example: Michael McGlen rolls two dice for the Sneak check described above. He gets a 2 and a 5. The 5 is a success, giving him a total of one success. Since the Sneak check had no listed difficulty, it is assumed to be 1. Michael has enough successes to pass the check.
There are four types of special skill checks that players should be aware of: Evade checks, Horror checks, Combat checks, and Spell checks. Each of these special skill checks are based on one of the six skills listed above and are described later in this rulebook. If an investigator receives a bonus to a skill, any special checks based on that skill also receive this bonus.
However, if an investigator receives a bonus only to a special check, that bonus does not apply to any other checks based on the same skill.
For example, Evade checks are a special type of Sneak check. A Skill card that gives +1 Sneak is useful both for Sneak and Evade checks. However, an item that gives +2 to Evade checks is only useful when making Evade checks. That bonus cannot be used on a normal Sneak check.
Spending Clue Tokens on Skill Checks
Clue tokens represent information about the Mythos threat that an investigator may acquire. A player may spend Clue tokens, one at a time, after any skill check (failed or not). Each spent Clue token allows the player to roll one additional die; if the result is a success, it is added to the total from the original roll.
Example: Joe Diamond fails a Lore (-1)  check, but gets two successes. Deciding that he really needs to pass this check, he discards one Clue token and rolls another die, getting a 3. Still no success, so Joe spends a second Clue token and rolls a second die, this time getting a 6. This extra success increases his total number of successes for the check to 3, enough to pass the check.
Important: Spending a Clue token always gives you the bonus dice that you are entitled to, even if the modifier has dropped the number of dice you can roll below 0.